1. Field of the Invention
The instant disclosure relates to a copper foil having carrier foil; in particular, to a peelable cooper foil structure having blackened ultra-thin foil and the manufacturing method thereof.
2. Description of Related Art
As the electronics industry trends towards lighter, thinner and more miniaturized electrical components, higher demand for precise circuitry and thin copper foil such as electrodeposited copper foil is necessary. Electrodeposited copper foil including a carrier foil is commonly used in the electronics industry for high precision and density circuitry in printed circuit board assemblies.
Generally speaking, electrodeposited copper foil including a carrier foil is categorized by peelable type and etchable type. Peelable type is defined by physically removing the carrier foil after the formation of the copper clad laminate substrate while the etchable type is defined by chemically removing the carrier foil after the formation of the copper clad laminate substrate. However, the demand for the etching process is becoming less significant.
The traditional electrodeposited copper foil includes a carrier foil (copper or aluminum foil), a release layer generally formed from metal oxides onto the carrier foil, and a super-thin copper foil generally formed on the release layer. When the carrier foil is physically removed from a super-thin copper foil, the surface of the super-thin copper foil will display a shiny appearance. However, when the super-thin copper foil is applied on inner layers of the multilayer circuit board, a blackening or browning process is required to provide the super-thin copper foil a blackened or browned appearance and enhanced bonding with the substrate formed thereon afterwards.
During the manufacturing of printed circuit board, high density and precision circuitry components such as microvias having diameter of less than 200 m generally requires laser drilling. However, due to the shiny surface of the super-thin copper foil, laser rays tends to be reflected, and excess operation of the laser is required, thus rendering higher energy consumption or multiple attempts are required to form the microvias. Furthermore, during high temperature compression process, the temperature of the super-thin copper foil is as high as 300° C., and the metallic bonding formed via an oxidation-reduction reaction between the metal oxides and the copper metal may affect consistency in peeling strength, thus affecting the peeling properties of the carrier foil and the super-thin copper foil.
To address the above issues, the inventor strives via associated experience and research to present the instant disclosure, which can effectively improve the limitation described above.